Motor driving device

Abstract

A motor driving device includes: a rotor position detector that detects a rotor position of the motor; a first waveform generator that generates a first reference waveform based on the rotor position; a second waveform generator that generates a second reference waveform based on the rotor position, the second reference waveform being different from the first reference waveform; a waveform outputter that outputs, as an output waveform, the first reference waveform, the second reference waveform, or a composite waveform of the first reference waveform and the second reference waveform, based on the torque command value; and a current supplier that supplies, to the motor, a motor current generated based on the output waveform. In the motor driving device, the waveform outputter changes a composite ratio between the first reference waveform and the second reference waveform in the composite waveform, according to the torque command value.

1 . A motor driving device that drives a motor based on a torque command value, the motor driving device comprising:
 a rotor position detector that detects a rotor position of the motor;   a first waveform generator that generates a first reference waveform based on the rotor position;   a second waveform generator that generates a second reference waveform based on the rotor position, the second reference waveform being different from the first reference waveform;   a waveform outputter that outputs, as an output waveform, the first reference waveform, the second reference waveform, or a composite waveform of the first reference waveform and the second reference waveform, based on the torque command value; and   a current supplier that supplies, to the motor, a motor current generated based on the output waveform, wherein   the waveform outputter changes a composite ratio between the first reference waveform and the second reference waveform in the composite waveform, according to the torque command value.   
     
     
         2 . The motor driving device according to  claim 1 , wherein
 the current supplier further includes a current detector that detects the motor current, and   the current supplier controls the motor current detected by the current detector to approximate a waveform of the motor current to the output waveform.   
     
     
         3 . The motor driving device according to  claim 1 , wherein
 the waveform outputter:   outputs the first reference waveform when the torque command value is less than a lower composite limit;   outputs the second reference waveform when the torque command value is greater than an upper composite limit; and   outputs the composite waveform when the torque command value is greater than or equal to the lower composite limit and less than or equal to the upper composite limit.   
     
     
         4 . The motor driving device according to  claim 3 , wherein
 the waveform outputter receives, as an input, a lower-limit setting value corresponding to the lower composite limit, and   the waveform outputter sets the lower composite limit based on the lower-limit setting value.   
     
     
         5 . The motor driving device according to  claim 3 , wherein
 the waveform outputter changes an amplitude of the first reference waveform according to the torque command value when the torque command value is less than the lower composite limit.   
     
     
         6 . The motor driving device according to  claim 1 , wherein
 the first reference waveform is a sinusoidal waveform.   
     
     
         7 . The motor driving device according to  claim 1 , wherein
 the second reference waveform is a trapezoidal waveform.   
     
     
         8 . The motor driving device according to  claim 1 , wherein
 the waveform outputter changes the composite ratio between the first reference waveform and the second reference waveform in the composite waveform, to different values in a stepwise manner according to the torque command value.   
     
     
         9 . The motor driving device according to  claim 1 , further comprising:
 a phase controller that receives, as an input, the torque command value, and changes a phase difference between the rotor position and the output waveform, based on the torque command value.   
     
     
         10 . The motor driving device according to  claim 9 , wherein
 the phase controller receives, as an input, phase setting information pertaining to the phase difference, and   the phase controller sets a relationship between the torque command value and the phase difference, based on the phase setting information.   
     
     
         11 . The motor driving device according to  claim 3 , further comprising:
 a phase controller that receives, as an input, the torque command value, and changes a phase difference between the rotor position and the output waveform, based on the torque command value, wherein   the phase controller changes the phase difference when the torque command value is greater than or equal to a phase change threshold, and   the phase change threshold is greater than or equal to the lower composite limit and less than or equal to the upper composite limit.   
     
     
         12 . The motor driving device according to  claim 1 , wherein
 the waveform outputter generates the composite waveform by performing weighted average on all phases of the first reference waveform and the second reference waveform.